如果您想从XML文件中检索特定的值

 XmlDocument _LocalInfo_Xml = new XmlDocument();
            _LocalInfo_Xml.Load(fileName);
            XmlElement _XmlElement;
            _XmlElement = _LocalInfo_Xml.GetElementsByTagName("UserId")[0] as XmlElement;
            string Value = _XmlElement.InnerText;

public void ReadXmlFile()
{
    string path = HttpContext.Current.Server.MapPath("~/App_Data"); // Finds the location of App_Data on server.
    XmlTextReader reader = new XmlTextReader(System.IO.Path.Combine(path, "XMLFile7.xml")); //Combines the location of App_Data and the file name
    while (reader.Read())
    {
        switch (reader.NodeType)
        {
            case XmlNodeType.Element:
                break;
            case XmlNodeType.Text:
                columnNames.Add(reader.Value);
                break;
            case XmlNodeType.EndElement:
                break;
        }
    }
}

可以避免使用第一个语句，只在XmlTextReader的构造函数中指定路径名。

LINQ to XML示例:

// Loading from a file, you can also load from a stream
var xml = XDocument.Load(@"C:\contacts.xml");


// Query the data and write out a subset of contacts
var query = from c in xml.Root.Descendants("contact")
            where (int)c.Attribute("id") < 4
            select c.Element("firstName").Value + " " +
                   c.Element("lastName").Value;


foreach (string name in query)
{
    Console.WriteLine("Contact's Full Name: {0}", name);
}

参考:LINQ到XML在MSDN

There are different ways, depending on where you want to get. XmlDocument is lighter than XDocument, but if you wish to verify minimalistically that a string contains XML, then regular expression is possibly the fastest and lightest choice you can make. For example, I have implemented Smoke Tests with SpecFlow for my API and I wish to test if one of the results in any valid XML - then I would use a regular expression. But if I need to extract values from this XML, then I would parse it with XDocument to do it faster and with less code. Or I would use XmlDocument if I have to work with a big XML (and sometimes I work with XML's that are around 1M lines, even more); then I could even read it line by line. Why? Try opening more than 800MB in private bytes in Visual Studio; even on production you should not have objects bigger than 2GB. You can with a twerk, but you should not. If you would have to parse a document, which contains A LOT of lines, then this documents would probably be CSV.

我写这条评论，是因为我看到了大量使用XDocument的示例。XDocument不适用于大型文档，或者当您只想验证内容是否为XML有效时。如果希望检查XML本身是否有意义，那么需要Schema。

我对建议的答案也投了反对票，因为我相信它本身就需要上述信息。假设我需要验证200M的XML是否有效，每小时10次。XDocument会浪费大量的资源。

prasanna venkatesh还指出，您可以尝试将字符串填充到数据集，它也将指示有效的XML。

您可以使用数据集读取XML字符串。

var xmlString = File.ReadAllText(FILE_PATH);
var stringReader = new StringReader(xmlString);
var dsSet = new DataSet();
dsSet.ReadXml(stringReader);

发布这篇文章是为了提供信息。

例如，检查XmlTextReader类。